The present invention relates generally to hearing testing probes placed within ear canals that are coupled to an instrument that monitors the condition within the ears. More specifically, the present invention provides a hearing testing probe with a user-replaceable coupling member for interfacing to an ear canal. The present invention further relates generally to a digital interface for coupling a testing instrument to a hearing testing probe placed within the ear canal. More specifically, the present invention relates to a hearing tester which emits test signals into the ear via a digital interface and through a probe placed within the ear canal, and then uses the response to make a determination of hearing function.
Hearing test devices that monitor the condition within a human ear are known. Such test devices generally require that the person performing the test (the “operator”) place a test probe of the device within the ear canal of a test subject. Once the probe is placed properly within the ear canal, the operator activates the device, usually by pressing a button or the like. The device then emits test signals into the subject's ear through the probe in the ear canal. In response to the test signals emitted, the device receives response signals from the ear, likewise through the probe in the ear canal. Such response signals received are then used to determine whether the ear is functioning properly.
Audiological testing for hearing impairment commonly requires an acoustic, air pressure, or vibratory stimulus to be presented to the test subject. Several of the methods for hearing evaluation require the use of a probe to generate and couple the stimulus directly to the subject's ear canal. Examples of hearing tests using these probes include otoacoustic emissions, acoustic immittance, acoustic reflex, reflectance, and, in some cases, auditory brainstem response. For each of these tests, certain characteristics of the stimulations need to be applied accurately in order to provide an accurate evaluation of the results.
In order to provide an accurate evaluation of the results, frequency response, magnitude, distortion, and other characteristics of the stimulus should be presented appropriately and measured accurately. Current calibration methods become less accurate as the frequency of the desired stimulus increases. Calibration errors become increasingly more significant at frequencies beyond 6 kHz and provide for a much reduced degree of certainty and consistency in measurements of hearing function. While it is desirable to perform measurements at higher frequencies, where often the first indications of hearing loss would be present, the ability to perform repeatable and consistent measurements with currently available commercial hearing testing probes is significantly limited.
For many tests, otoacoustic emissions testing in particular, the levels of stimulus applied to the ear canal of the subject is determined by a calibration sequence performed when the probe is placed into the ear canal of the subject. This calibration of the probe response in the subject's ear canal is critical to determining and applying the appropriate stimulus. Assessment and diagnosis of the test responses are based on the levels of the stimulus applied, and thus the accuracy of the assessment is compromised if the applied levels are not accurate.
During hearing testing, a seal to the ear canal is provided by an eartip containing one or more internal sound channels for conducting sound to and from the end of the probe to the ear. FIG. 1 illustrates an exemplary recessed probe design as is known in the art. The accuracy of the calibration with the commonly available hearing test probes is limited by an intentional design feature. The end of the hearing test probe, where the stimulus exits into the ear canal, is recessed from the end of the eartip. This recess, usually two to three millimeters in length, provides a place for contamination (e.g., cerumen or other biological material) to collect without entering the body of the probe where cleaning or extraction of the contamination would be difficult and can compromise the performance of the probe.
Referring to the exemplary recessed probe design illustrated in FIG. 1, the recessed probe end provides a buffer zone that often contains any contamination and reduces the occurrence of infiltration into the probe body. However, the recessed tip design is not desirable for performing hearing testing at high frequencies because of known errors in performing calibration at high frequencies associated with recessed probe tips.
Evidence of the difficulty in managing contamination in hearing test probes can be seen in recent probe designs where the ear canal end of the probe is made to be user replaceable in the event that contamination gets beyond the recess at the front of the eartip and enters the body of the probe. This solution can provide a more convenient means of contamination removal than many of the cleaning and disassembly procedures used in older designs. However, the cost of the replacement component can be significant even though it is only likely to require replacement after the testing of numerous subjects. This problem would be significantly exacerbated if the probe end is designed to exit flush with, or extend slightly beyond, the end of the eartip.
FIG. 2 illustrates an exemplary replaceable probe tip design as is known in the art. Existing replaceable probe tip designs commonly use a recessed tip design to minimize the occurrence of contamination. As noted above, the recessed tip design is not desirable for performing hearing testing at high frequencies because of known errors in performing calibration at high frequencies associated with recessed probe tips. Additionally, existing replacement probe tips are too expensive and cumbersome to replace frequently.
Another limitation in current hearing probe designs is the minimal area available for the stimulus and microphone acoustic channels through the eartip. A three millimeter outer diameter limitation is the industry standard such that the eartips are small enough to properly fit and seal to the ear canals of infants and newborns. This minimal cross-sectional area of the stimulus and microphone channels causes limitations in the frequency response of the stimulus sources and increases the impedance of the microphone input which causes an increase in its noise floor. Compounding this limitation is the need for the stimulus channels and the microphone channels maintain separation to their exit at the ear canal. Maximizing the use of the three millimeter diameter allowed provides for an improved frequency response and noise floor.
Additionally, existing hearing test instruments typically communicate test signals to a probe and receive the acoustic response signals from the probe in real-time. As such, these existing hearing test devices have been limited to performing a hearing test on one ear at a time.
Also, existing hearing test instruments have been limited in the manner of communication between the probe and the instrument. Specifically, existing hearing test instruments have communicated with the probe using analog electrical signals over a cable. However, the cables used in existing hearing test instruments have limited cable lengths, requiring the patient and tester to be in close proximity and reducing flexibility in probe placement. The limited cable length is largely due to the need to minimize signal degradation when using analog transmissions for the stimulus and responses. The cable is shielded to minimize interference from outside radio frequency (RF) and electromagnetic interference (EMI).
The construction of this communication cable is complicated by the requirement to eliminate interference between the stimulus channels and the microphone channel. The probe cable adds bulk and weight to the system and may pull on the probe in the ear during testing, making it difficult to keep the required seal and positioning in the ear canal.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.